Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Ocular hypertension and glaucoma are conditions of the eye characterized by, or resulting from, increased intraocular pressure (IOP). Those afflicted with ocular hypertension exhibit higher than normal IOP in the absence of optic nerve damage or visual field loss, while glaucoma describes a group of ocular disorders displaying characteristic IOP-associated optic neuropathy. Elevated IOP is the most important risk factor for glaucoma, so those with ocular hypertension are frequently considered to have a greater chance of developing the condition. Over time, increased IOP can lead to permanent damage of the optic nerve and resultant visual field loss, which, if left untreated, can progress to blindness.
Intraocular pressure is primarily dictated by the liquid aqueous humor, which is produced by the ciliary body of the eye. Changes in the balance between the production of the aqueous humor and the drainage of the fluid through the trabecular meshwork in the eye can increase the pressure within the eye (i.e., IOP). Routine measurement of IOP can be used to diagnose hypertension and glaucoma, which guide treatment regimens using a range of drugs (for example, the aryl- and alkyl-sulfonamides, which inhibit carbonic anhydrase and decrease intraocular pressure). Normal IOP is typically between 10 mmHg and 21 mmHg.
Intraocular pressure is typically measured during comprehensive eye examinations using various techniques, most notably tonometry. These measurements are typically conducted by ophthalmologists, optometrists, clinicians or other trained professionals using a tonometer in clinical offices. A variety of different tonometers have been developed. Some devices are hand-held, but many are large enough to restrict their portability (for example, the rebound tonometer). Because operation of these devices requires technical training, a visit to a physician's office is required, which can be inconvenient for the patient. Moreover, there are several situations where access to ophthalmologists or traditional tonometry devices are very limited or even unavailable, such as, in developing countries and rural or other limited health care environments, in emergency rooms, or in remote clinical sites. Current tonometry tests are also fairly invasive, involving direct contact with the eye to take a pressure measurement, or puffed air, which often causes the patient to flinch or blink. In some cases, multiple attempts must be made to obtain readings, which can be very difficult for children and infants, who can be restless and uncooperative. Further, fitness, exercise, nutrition (e.g. caffeine, alcohol, and glycerol), the time of day, and other variables can influence intraocular pressure, which poses challenges to one-point measurements that must be made in a physician's or optometrist's office.